For harcore HP fans out there: I have a mission for tu :)

Okay, lately my friend told me that "Harry Potter fans are basically a cult." ... I had no idea what a cult was. So i looked it up and found that it was"a group o sect bound together por veneration of the same thing, person, ideal, etc." And when I admitted to him that I didnt know what it meant until I looked it up, he insulted hp fans because he was pretty sure that the series even mentioned the word cult at least once. So I made a deal with him, and now if he finds the word cult in the series (he's gonna re-read all the books) then i'll have to do something that he'll make up for me (like a dare almost) so now im nervous wondering if the word really IS in the series, so can anyone help me buscar for it? i'd really apreciate it! if anyone finds it tell me what book and what page :D thanks! have fun on ur mission!!! :)
ps: sorry, i know this doesnt invole the HP vs Tw*l*ght battle, but i really need help on this